1) In ecosystems, why is the term cycling used to describe material transfer, whereas the term flow is used for energy exchange?
A) Both material and energy are recycled and are then transferred to other ecosystems as in a
flow.
B) Materials are repeatedly used, but energy flows through and out of ecosystems.
C) Materials are cycled into ecosystems from other ecosystems, but energy constantly flows
within the ecosystem.
D) Both material and energy flow in a never-ending stream within an ecosystem.
E) None of the choices is correct.
2) Green fluorescent protein (GFP) can be used to fluorescently label a specific protein in cells by
genetically engineering cells to synthesize the target protein fused to GFP. What is the advantage of using GFP fusions to visualize specific proteins, instead of staining cells with fluorescently labeled
probes that bind to the target protein?
A) GFP fusions enable one to track changes in the location of the protein in living cells; staining
usually requires preserved cells.
B) GFP fusions are not subject to artifacts; fluorescent probes may introduce background
artifacts.
C) GFP permits visualization of protein-protein interactions; fluorescent probes do not.
D) GFP fusions enable higher resolution than staining with fluorescent probes.
E) GFP permits the position of the protein in the cell more precisely than fluorescent probes.
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